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Wed, 14 Aug 2024 17:19:46 -0700 (PDT) MIME-Version: 1.0 References: <20240813215358.2259750-1-shakeel.butt@linux.dev> <5psrsuvzabh2gwj7lmf6p2swgw4d4svi2zqr4p6bmmfjodspcw@fexbskbtchs7> In-Reply-To: From: Nhat Pham Date: Wed, 14 Aug 2024 17:19:35 -0700 Message-ID: Subject: Re: [PATCH v2] memcg: use ratelimited stats flush in the reclaim To: Yosry Ahmed Cc: Shakeel Butt , Jesper Dangaard Brouer , Andrew Morton , Johannes Weiner , Michal Hocko , Roman Gushchin , Muchun Song , Yu Zhao , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Meta kernel team , cgroups@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Stat-Signature: grp7fzspcs336imhej4pdi77jqh7z7cu X-Rspam-User: X-Rspamd-Queue-Id: 1008E18000A X-Rspamd-Server: rspam02 X-HE-Tag: 1723681186-20868 X-HE-Meta: U2FsdGVkX1/Bs6PBeWSi/1uz3ZvfdDE8+B5JYr1509bq5PVuvTLraxkff7WPFn/vE5A5YxRdEQx7QDrjvIQws3nG68xv/26DJOfJ832S8y6AXf0A4IZ+mNrEPeO4RgfCeQDhiGEPx+xDDZVNsw4gpLK2iZxhdadfJ5yyoZDms0U3Tpjslv3hLIQ+i2hxeOoCyXdWNvyXlbWA2un3IW7B9Cs/8DcV2sfrHfHu5X2+lkyWOtYLDu4XzJhJ9W0JVHNQuZK8DqWMFF3TeDxB0KMNj/GzQYAv1PbGC8nlxvQyIeT4QqTCBWSWa6pA2ehMtQOfwMErrEbPV0ZFf+1oEl6H6Gll6xa3ToluCU/Rt9pVE7IAnL120vo9JDctrR30X1I4JYpwbEO1KNeicbX0ZooBkq8S2HgPzt4AEnFxUFqtpzXl9hZ9wvcLY3Q6a/DeeLvVrsh05IYuGYqvGMTy/u05c3/DZJ68Ik5dJ/FS3mw3IQNCJ306T3lAI0SP8wNvpUOe9lI/naVH6DvN0q6H3/E0Wf/pBvf2yNgu6OAkpY/4WRp/s7LQGHGScP32s5YI7PXcU+iPs2Qt0uYS0wHUiiy6xBMNz7OBpqt8mXy4hEVvpe1VswRQCW+mDb2t5U5m3WynHBMr1LHp3mnoZcHFsVvD2/U7qcCB8mN0+dX6r1g5KGNVf0QoMtvBcVZOI8uyRA4FlsxOfqU7UBN58H0AXJ2DcRs33IAlAp/BoxIQg3HY+b4FexMMoXqD9bNudg1jQfX6xqc+PSDEO/drFrxDrC4TUfvj47wjciNUUyEvL01zigrxPNvVa40PVpUDy2BdVP84NqzBqZQUpKxFMFLn5UEmFxMuwgFN90zKxxqhvcdh4fQqlbuIn5Jvprw4jcNxEYf5lBHUjtO/XPEoPqQWqQCSKn7EG+rRIVwFRsZbCst/Uxz0/t57zCfUThsJxw0Rl8tfmiMM6WnJjcCiT3cGmt3 bB06ZkQY w4QX1s4EMchqxNhEOA3Z7uCXxELjg6xjpcJnYECqOi5mjL4fUbgkWQ2F14hJxsMY9XTrIgCKXldvzyVOQ5XbW/GDtG49bcrr2UmcpD/ReCsVyGoW/chrTcGw0E+wMeawo/9O9lcGNkwZERiJe29EA5/VJtp8iWApIQRuSkrQ2fiocs8diVE8wEgYUX88ECYmicypsmkUhTWg+WqefTg8GdGELaHqFQrm2Wgr8TanQyUHY4d7mvSjhduu1yYjkgAZSV5kjNeUjzxcbaYpni2E45V9+62JxvzutTBXRUPPRky8k5hIfVE/L4+tdk7L53FSKOXZ/ X-Bogosity: Ham, tests=bogofilter, spamicity=0.380140, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Aug 14, 2024 at 4:49=E2=80=AFPM Yosry Ahmed = wrote: > > > We can also use such atomic counters in obj_cgroup_may_zswap() and > eliminate the rstat flush there as well. Same for zswap_current_read() > probably. zswap/zswapped are subtree-cumulative counters. Would that be a problem? > > Most in-kernel flushers really only need a few stats, so I am > wondering if it's better to incrementally move these ones outside of > the rstat framework and completely eliminate in-kernel flushers. For > instance, MGLRU does not require the flush that reclaim does as > Shakeel pointed out. > > This will solve so many scalability problems that all of us have > observed at some point or another and tried to optimize. I believe > using rstat for userspace reads was the original intention anyway. But yeah, the fewer in-kernel flushers we have, the fewer scalability/lock contention issues there will be. Not an expert in this area, but sounds like a worthwhile direction to pursue.